SN74ALS843NT Equivalent & Substitute Parts

Part Overview

The SN74ALS843NT is a D-Type Transparent Latch IC with 9-bit configuration and tri-state output, manufactured by Texas Instruments in the 74ALS logic series. This component is classified as obsolete, which necessitates identification of functionally equivalent alternatives for ongoing design support and procurement. The part operates within a 4.5V to 5.5V supply voltage range and is housed in a 24-DIP through-hole package. Due to its obsolete status, equivalent substitute parts with identical electrical characteristics but different packaging options are available to maintain design continuity.

Substiute Parts

SN74ALS843NT

Texas InstrumentsIn Stock: 1051SN74ALS843NT Datasheet

Current PartRFQ

SN74ALS843DWR

Texas InstrumentsIn Stock: 1043SN74ALS843DWR Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the SN74ALS843NT is determined by strict equivalence across the following critical parameters:

• Logic Type: D-Type Transparent Latch (identical function)
• Circuit Configuration: 9:9 (identical bit width and channel arrangement)
• Output Type: Tri-State (identical output control capability)
• Voltage - Supply: 4.5V ~ 5.5V (identical operating voltage range)
• Independent Circuits: 1 (identical circuit count)
• Delay Time - Propagation: 5ns (identical timing specification)
• Current - Output High, Low: 2.6mA, 24mA (identical drive capability)
• Operating Temperature: 0°C ~ 70°C (identical temperature range)
• Series: 74ALS (identical logic family)
• RoHS and REACH Compliance: ROHS3 Compliant, REACH Unaffected (identical regulatory status)

The primary difference between the main part and its substitute is the mounting technology and package form factor. The SN74ALS843NT uses through-hole mounting (24-DIP), while the SN74ALS843DWR uses surface-mount technology (24-SOIC). Both parts share identical electrical performance and are manufactured by Texas Instruments from the same base product number (74ALS843).

Parameter Comparison

Engineering Selection Recommendations

The SN74ALS843DWR is the direct electrical equivalent of the SN74ALS843NT. Selection between these parts is determined by PCB assembly requirements and manufacturing process:

• For through-hole assembly designs: The SN74ALS843NT (24-DIP) maintains compatibility with existing through-hole PCB layouts. However, due to obsolete status, long-term availability is limited.

• For surface-mount assembly designs or new designs: The SN74ALS843DWR (24-SOIC) is the preferred selection. This part is active in production, ensuring sustained availability and supply chain reliability. The surface-mount package is compatible with modern PCB assembly processes.

Both parts carry identical RoHS3 compliance and REACH unaffected status, meeting current regulatory requirements. The electrical performance, timing characteristics, and operating parameters are functionally identical, ensuring drop-in compatibility at the circuit level when package footprint and assembly process constraints are accommodated.

Frequently Asked Questions (FAQ)

Q: Can the SN74ALS843DWR directly replace the SN74ALS843NT in an existing design?

A: Electrical substitution is complete. The SN74ALS843DWR provides identical logic function, timing, and electrical performance. However, physical replacement requires PCB redesign due to different package types (24-SOIC surface-mount versus 24-DIP through-hole). The parts are not pin-compatible for direct socket substitution.

Q: Why is the SN74ALS843NT listed as obsolete?

A: The SN74ALS843NT is classified as obsolete by Texas Instruments. The SN74ALS843DWR (24-SOIC variant) remains in active production, representing the current manufacturing standard for this logic function.

Q: Are there any electrical performance differences between the two parts?

A: No. Both parts share identical specifications for logic type, circuit configuration, output type, supply voltage range, propagation delay, output current ratings, and operating temperature range. Differences are limited to package form factor and product status.

Q: What are the package dimension differences?

A: The SN74ALS843NT uses a 24-DIP package measuring 0.300" (7.62mm) in width. The SN74ALS843DWR uses a 24-SOIC package measuring 0.295" (7.50mm) in width. Both packages contain 24 pins with identical electrical pin assignments.

Q: Are both parts RoHS and REACH compliant?

A: Yes. Both the SN74ALS843NT and SN74ALS843DWR are ROHS3 compliant and REACH unaffected, meeting current environmental and regulatory standards.

Q: What is the moisture sensitivity level for these parts?

A: Both parts have a Moisture Sensitivity Level (MSL) of 1, indicating unlimited shelf life without moisture control requirements.